Probing trade-off between critical size and velocity in cold-spray: An atomistic simulation

TL;DR

This study uses molecular dynamics simulations to explore bonding mechanisms in cold spray at the nanoscale, revealing the importance of high velocities, substrate thermostating, and stress oscillations, with implications for electronics manufacturing.

Contribution

It demonstrates the validity of existing models at the nanoscale and introduces a method for high-velocity spray and stress analysis in cold spray processes.

Findings

High spray velocities are needed for jet formation at the nanoscale.

Oscillatory stress behavior propagates into particles during cold spray.

Formation of titanium silicide suitable for electronic applications.

Abstract

The detailed mechanism of bonding in the cold spray process has remained elusive for both experimental and theoretical parties. Adiabatic shear instability and hydrodynamic plasticity models have been so far the most popular explanations. Here, using molecular dynamics simulation, we investigate their validity at the nanoscale. The present study has potential application for the fabrication of ultra-thin layers for the electronics industry. For this aim, we considered Ti nanoparticles of different diameters and Si substrates of different orientations. It is shown that very high spray velocities are required for a jet to be observed at the nanoscale. We propose a method for thermostating the substrate that enables utilizing high spray velocities. For the first time, we demonstrate an oscillatory behavior in both the normal and radial stress components within the substrate that can propagate into the particle. We have shown that neither the adiabatic shear instability model nor the hydrodynamic plasticity model can be ignored at the nanoscale. Besides, the formation of a low-resistance titanium silicide proper for electronic application is illustrated.